Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-08-29
2003-09-09
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C252S182200, C560S025000, C156S275500, C427S508000, C522S090000, C522S096000, C428S423100
Reexamination Certificate
active
06617413
ABSTRACT:
The invention relates to compounds having isocyanate groups with or without blocking, allophanate groups and free-radically polymerizable C—C double bonds, the C—C double bonds being in activated form by virtue of a carbonyl group attached directly to them or by virtue of an oxygen atom in ether function (referred to for short below as activated double bonds), derived from polyisocyanates and alcohols A which, in addition to the alcohol group, also carry an activated double bond (compounds I).
The invention additionally relates to radiation-curable formulations and coating compositions which comprise the compounds I, to methods of coating with these substances, and to coated articles produced by these methods.
Coating compositions based on compounds containing isocyanate groups are common knowledge, for example, in the form of two-component coating materials (cf. Kunststoff Handbuch, Volume 7, Polyurethane, 2
nd
edition, 1983, Carl-Hanser-Verlag Münich Vienna, pages 540-561). Industrial processors of coating systems, such as the coatings industry, expect said systems to meet a diverse profile of requirements. These requirements relate both to the processing properties and the service properties.
In terms of the processing properties it is very important that the coating systems combine a very low solvent content with a low viscosity. The low viscosity is required so that the coating materials can be applied without problems by customary techniques, such as by spraying, to the surface that is to be coated. The solvent content of these coating materials causes problems in that, when the coating materials are being processed, technically complex measures must be taken to ensure that the solvents released when the coating materials are applied and are drying are not emitted into the atmosphere.
Furthermore, it should be possible to cure the articles provided with the coating compositions by means of UV irradiation. In particular, following brief irradiation with relatively low radiation doses, the hardness should increase dramatically, but without longer irradiation leading to a further marked increase in hardness. With the prior art systems this hardening can be brought about only at very high radiation doses; in other words, the required dwell times in the existing irradiation units are still too long. There is therefore a need for systems having groups which on exposure to very low radiation doses, i.e. short exposure times, are consumed near-quantitatively in a polymerization reaction.
Furthermore, processors are increasingly calling for what are known as dual-cure systems. The feature of these systems is that they can be cured both by radiation and by means of a second, independent curing mechanism. There is a particular desire for systems which, following application of the coating composition, can be initially cured by very brief exposure to UV light to form a dust-dry film. Over the course of several days this film should then cure further, simply by storing it in air at room temperature or with heating, until a hard film is formed which has the ultimate desired service properties. This type of dual-stage curing is particularly important since it gives the processors of the coating systems the option to coat an article with a film in a first working step and then to process this film further in a second working step; in particular, to give the coated article following irradiation a defined profile using pressure. At the time of their deformation in the second working step, therefore, the films or foils must be already cured, so that they do not stick to the tools in the course of deformation; on the other hand, however, they must not be so hard as to crack when extended and deformed. The coated articles produced in this way must be stored for a while thereafter until the coating has attained its ultimate service properties.
As far as the service properties are concerned, particular requirements here are as follows.
insensitivity to mechanical stress such as tension, extension, impact, scratching or abrasion;
resistance to moisture (e.g., in the form of water vapor), solvents, petrol and dilute chemicals, as well as chemical environmental influences such as sulfuric acid rain, pancreatine, tree resin;
resistance to environmental influences such as temperature fluctuations and UV radiation;
high gloss of the coated surfaces;
good adhesion to a variety of substrates such as
good adhesion to a variety of substrates such as substrates coated beforehand with primers, fillers, color effect layers or other coatings, and also directly to plastics, wood, woodbase materials, paper, glass, ceramic, textiles, leather or metal.
A further requirement is complete curability of unexposed or non-radiation-curable areas of the coating materials, for example in shaded regions of, for example, three-dimensional substrates such as vehicle bodies or pores in wood, paper, foams, ceramic materials, in coating materials containing radiation-absorbing ingredients such as pigments, UV absorbers, fillers, and of spray mist deposits. Curing is intended to take place in the course of storage in air or with additional heating or baking.
The applications DE-A-19741781 and DE-A-19814874, which were not published before the priority date of the present specification, relate to radiation-curable prepolymers which contain urethane groups and are used as coating compositions. However, they contain no free isocyanate groups.
U.S. Pat. No. 5,300,615 and U.S. Pat. No. 5,128,432 likewise disclose polyurethanes having free-radically polymerizable double bonds, but these likewise carry no free isocyanate groups.
EP-A-549116 and DE-A-3819627 relate to compounds which include both isocyanate groups and free-radically polymerizable C—C double bonds. These compounds are prepared by dimerizing or trimerizing commercially customary aliphatic isocyanates to give their counterparts having uretdione, isocyanurate or biuret groups, and then reacting these dimers and/or trimers with hydroxyalkyl acrylates. A disadvantage of these systems is that they have a very high viscosity and can be processed only with the addition of large amounts of solvent.
U.S. Pat. No. 5,739,251 likewise discloses urethanes formed from alcohols and comprising beta,gamma-ethylenically unsaturated ether groups, which are virtually free from isocyanate groups, and discloses allophanates derived from these urethanes.
These beta,gamma-unsaturated compounds, however, have the particular disadvantage of a high viscosity, and cannot per se be cured by means of UV radiation.
It is an object of the present invention to provide compounds which can be used to produce coating systems having the abovementioned profile in respect of the processing and service properties. In particular, the coating systems should possess a low viscosity at low solvent content and should be suitable for use as dual-cure systems whose radiation curing can be carried out completely (or until freedom from tackiness or scratch resistance of the films) with relatively low radiation doses.
We have found that this object is achieved using the compounds I of the invention which are in general essentially free from uretdione, biuret or isocyanurate groups.
Preferred compounds I are, therefore, those of the formula I
OCN—R
1
—(—R
2
—C(O)—R
2
—R
1
—)
n
—NCO I
in which
n is an integer from 1 to 10, preferably from 1 to 5
R
1
is a divalent aliphatic or alicyclic C
2
-C
20
hydrocarbon unit or an aromatic C
5
-C
20
hydrocarbon unit
R
2
in each repeating unit is —NH— once and N—C(O)—R
3
once, R
3
being a radical derived from an alcohol by abstracting the hydrogen atom of the alcoholic hydroxyl group, and the alcohol carrying functional groups including, in addition to the alcohol group, an activated double bond.
The radicals R
1
are preferably those derived by extracting the isocyanate group from customary aliphatic or aromatic polyisocyanates. The diisocyanates are preferably aliphatic isocyanates of 4 to 20 carbon atoms. Examples of customary diisocyanates are aliphatic diisocy
Beck Erich
Bruchmann Bernd
Königer Rainer
Lokai Matthias
Reich Wolfgang
BASF - Aktiengesellschaft
Gorr Rachel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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